Scientists at the
Australian Institute of Sport have developed a jacket for pre-cooling
athletes before endurance events in the heat. The jackets are made from
wet-suit material and are packed with ice. Athletes who wore the jackets at
the Atlanta Olympics probably boosted their output power by 1-2%.

Hot or humid environmental conditions have a negative effect onendurance
performance (e.g., Galloway andMaughan, 1997). Any
strategies that delay or reduce the increasein body temperature during
exercise are therefore likely to enhanceperformance in the heat. In this
article we summarize research on theeffectiveness of one of these strategies,
pre-event cooling. We alsodiscuss a series of studies completed at the AustralianInstitute
of Sport (AIS) that led to the development of a coolingjacket
subsequently used by many Australian Olympians during the 1996Summer Olympic
Games in Atlanta.

Research onPre-cooling

The concept of reducing skin or core temperature prior toendurance
competition has been investigated since the early 1980s(see review by Booth et al., 1997). Lower skintemperatures enable a
greater temperature gradient for dissipatingheat from deeper regions of the
body (Schmidt etal., 1981). Cooler skin temperatures
mean that less of the totalcardiac output is directed toward the skin,
possibly allowing moreblood to be directed to active skeletal muscle. Lower
skin and coretemperatures can also delay the onset of sweating and decrease
sweatrate, resulting in a conservation of body water during a
prolongedcompetitive event (Hessermer et al., 1984).The
following published papers form the basis for the currentpre-cooling
practices used by athletes prior to competition in theheat.

Schmidt and Brück (1981) decreasedcore temperature
by 1ºC in 12 well-trained rowers and observedthat the heart rate and sweat
rate response to a progressive maximaltest was reduced in the pre-cooled
versus the control trial. In thisstudy all subjects rested at 28ºC for 30 min
prior to thebicycle test that was performed at 18ºC. Pre-cooling did
notaffect maximum oxygen uptake (VO2max)
or peakpower output.

Hessermer et al. (1984) used a similardesign but
incorporated a 60-min maximal cycling time trial for theirperformance test.
The eight well-trained rowers improved theiraverage power output by 6.8% when
the 60-min time trial was precededby a cold air pre-cooling maneuver that
decreased mean skintemperature by 4.5ºC.

Myler, Hahn & Tumilty (1989) investigatedthe
effects of pre-cooling on the ability of rowers to perform at30ºC and 30%
humidity. They found that performance of a 6-minmaximal rowing effort
improved significantly: after 5 min of icingthe skin, the rowers traveled 17
meters further in a 6-min all-outrowing test. The increase in power output
averaged ~3%.

Lee and Haymes (1995) observed improvements inrunning
performance following a pre-cooling procedure. Fourteenphysically fit male
runners were pre-cooled for 30 min using coldair. After a 10-min transition
period, during which skin temperatureswere allowed to warm, subjects ran
until exhaustion at 82%VO2max at 24°C.
Pre-cooling caused a0.37°C drop in core temperature and an improvement in
runningtime from 22.4 to 26.2 min, or 17%. (equivalent to about 1% in
anevent). The improved performance was associated with a decreasedsweat rate.

Impressed by the potential benefits of pre-cooling on
performance,scientists at the Australian Institute of Sport designed a
coolingjacket for their athletes. The jacket was made from wet-suit
material(Neoprene) and was designed to be packed with ice. In 1996 six
womencyclists who were members of the Australian National road cyclingsquad
agreed to use the prototype prior to a 25-km individual timetrial held in
Queensland, Australia. Not surprisingly, the cyclistsfelt noticeably cooler
and upper chest skin temperature was reducedimmediately following removal of
the jacket. After the race thecyclists documented their impressions of the
ice jacket by completinga questionnaire. Their suggestions were used to
modify the jacket forthe next prototype.

In collaboration with the Commonwealth Scientific and IndustrialResearch
Organization and the University of Sydney, the AIS nextrecruited nine
recreational cyclists to complete maximal gradedexercise tests on a bicycle
ergometer in a heat chamber at 32ºCand 60% humidity. The first trial was used
to familiarize thesubjects to the testing procedure. Subjects then completed
either acooling trial or a control trial in a cross-over fashion. For
thecooling trial the modified cooling jacket was worn for the first 9min of
the protocol (125-175 watts). Subjects cycled for an averageof 1.1 min longer
during the cooling trial (332 vs 341 watts).Thermocouples attached to the
mid-chest and the mid-back indicatedthat the skin temperature beneath the
cooling jacket decreased from32-35ºC down to 10-16ºC by the end of the 9-min
period.During the cooling trial perception of effort and perception ofthermal
comfort was significantly improved. Despite these differencesin perceptions
and skin temperature, the ice jacket did not affectrectal temperature, heart
rate, or blood lactate (Smithet al., 1997).

For the next study, four female and seven male rowers from theAustralian
Defense Force Academy completed two maximal 2000-mlaboratory trials on a
Concept IIb rowing ergometer in the AISenvironmental chamber (33ºC, 60%
humidity). Prior to the 2000-mtrials, rowers consumed 350 ml of water and
completed a 30-minwarm-up at 75% of the power output achieved during a
maximal effortfamiliarization trial. Prior to the start of the maximal
exercise, anextra 150 ml of water was consumed. For the pre-cooling trial,
afinal version Neoprene cooling jacket developed by Neptune Wetsuitswas worn
throughout the warm-up period and the rowers were informedthey were drinking
water. For the placebo trial red food coloring wasadded to the water and
rowers were told they were receiving glycerol,an agent that could aid in
hydration and improve performance.Following pre-cooling, average rowing times
decreased by 2.8 seconds,or 1.2%. In the cooling jacket trial there was less
of an increase incore temperature and lower sweat rates during the warm-up.
Followingthe warm-up period, rowers rated their thermal comfort
significantlybetter in the pre-cooling trial, and this improved thermal
comfortwas also apparent following the 2000-m rowing test. Similarly,
theperceived exertion following the rowing test was significantly
lower,despite an elevated post exercise blood lactate and a lower bloodpH.

The success of pre-cooling suggests that the duration and theintensity of
a warm-up should be limited so that core temperature isnot elevated prior to
competition. One of the primary advantages of acooling jacket may be that
this form of active cooling allows anathlete to experience
competition-specific exercise intensity duringthe warm-up without causing a
substantial increase in coretemperature.

AIS Jackets at the
1996Olympics

Feedback from coaches, athletes and sport scientists wasincorporated into
the Olympic version of the cooling jacket forAustralian athletes. It was left
up to each sport to evaluate rulesto ensure that the ice jacket would not be
considered illegal priorto Olympic competition. The proper contacts were made
and both Adidas(official Olympic clothing sponsor for Australia) and the
AustralianOlympic Committee agreed to support the use of the ice jacket
byAustralian Olympians. Once the administrative aspects of the projectwere in
order Olympic ice jackets were sent out to track cycling,mountain cycling,
road cycling, rowing, canoeing, hockey, and trackand field. Each sport then
refined the pre-cooling protocols for useprior to Olympic competition.

Approximately 200 green and gold ice jackets bearing theAustralian coat of
arms were produced for Olympic athletes travelingto Atlanta. Figure 2 shows
some of the rowing team in their jackets.Another 30-40 jackets were produced
for Australian athletes competingin the Para-Olympic Games. In all cases
athletes were not forced touse the ice jackets. Instead, athletes were made
aware of laboratorydata indicating the potential for beneficial effects and
then the useof ice jackets was incorporated into practice sessions. Quite
simply,many athletes liked the way the jackets felt when training
andcompeting in hot conditions.

Figure 2: Australian
rowing team wearing jackets at Atlanta in 1996.

Evaluation sheets were returned by 43 Olympic athletes and 7Olympic
coaches who used the cooling jackets in Atlanta. Athletes andcoaches
represented road cycling, mountain cycling, rowing, fieldhockey, and track
and field (mostly race walkers). Preliminary dataindicate that 90% of the
respondents used the cooling jackets duringtraining sessions and 80% used the
cooling jackets as an aid duringOlympic competition. All athletes who used a
cooling jacket duringcompetition indicated that it made a positive
contribution to theirperformance. Taking into account these comments and
previousresearch, we believe that the jackets enhanced the output power ofour
athletes by at least a percent or two, depending on the event andthe extent
of pre-cooling. Ice jackets will be used increasingly incompetitions held
under hot conditions.